The invention concerns a filter and frame arrangement, e.g., a HEPA type filter unit, and is particularly directed to the arrangement for sealing the filter in place to prevent contaminants from leaking around the filter. The invention here concerns an arrangement that both holds the filter in place in the unit and also seals the space between the unit's primary seal (e.g., gel seal) and the clean space.
High Efficiency Particulate Air (HEPA) filters are used extensively in industrial, commercial and residential applications to filter out dust and dirt from the air which can harbor harmful bacteria or other micro-organisms. These filters are capable of filtering out more than 99.99% of the particles in the air. One of the drawbacks to the HEPA filter is its high airflow pressure drop, especially as the filter starts to load up. Because of this, the air would prefer to bypass the filter as it always takes the path of least resistance. Since normal ambient air contains millions of particles per cubic foot, even the smallest leak will cause thousands of particles per minute to bypass the filter. Because these filters are used in critical applications, any leak can therefore result in grave harm to the people or product the filter is intended to protect. The filters become loaded up over time, and they have to be replaced periodically. This generally means that they have to be mounted into some sort of holding frame or conduit within the airstream. The sealing of these filters therefore becomes critical.
Most HEPA filters are held in place by any of various mechanical fasteners, which hold the frame of the filter against some sort of seal, e.g., a gel seal. These mechanical fasteners must hold against the airflow pressure that is trying to push the filter away from its seal, and have to maintain the seal integrity. However, once the seal has been compromised, any air leakage, and of course any entrained contaminates, can pass around the filter directly into the clean space.